The invention relates to the technical field of measuring the diameter of a vein of a patient by the Doppler effect.
The subject of the invention is applied particularly advantageously in the area of monitoring the blood volume of a patient.
In the above technical area, it should be borne in mind that management of hypovolemic shock involves rapid volume replacement. Hence physicians tend to infuse the patient rapidly with replacement fluids. Fluid overload frequently occurs, diluting the coagulation factors and thus increasing the risk of bleeding and tissue infiltration to create, for example, cerebral and pulmonary edema.
Hence there is a need to monitor changes in blood volume during this delicate therapeutic phase, essential for the patient.
Since blood volume is not currently measured in an effective manner, the idea emerged of evaluating the change in cross section of certain veins able to expand, such as the jugular or femoral vein, during volume replacement. Observing the change in diameter of a vein enables the level of vascular filling to be monitored and hence the filling rate to be determined.
Hence a device is needed to determine the change in diameter of an expanding vein to evaluate the blood volume replacement rate of a patient who may be under adverse environmental conditions, such a device being designed to be autonomous, small in size, and very easy to use.
The goal of the invention is thus to meet this need by offering a device for measuring the change in diameter of a vein by the Doppler effect.
According to the invention, the device has, in a housing:
at least one ultrasonic wave transmission and reception probe connected to a control and processing unit,
processing means as part of the control and processing unit that are designed to determine the difference in frequency between the transmitted and received ultrasonic waves,
a speaker connected to the output of the processing means,
a display means connected to the control and processing unit designed to display the change in diameter of the vein,
a means for generating a first signal triggering an operating phase of the transmission and reception probe in continuous mode,
a means for generating a second signal triggering an operating phase of the transmission and reception probe in discontinuous mode,
and a control and processing unit designed:
when generating the first signal, to control the transmission and reception probe in continuous mode in order to obtain an audible signal from the speaker as a function of the position of the transmission and reception probe relative to the vein in order to locate the vein, and
when the second signal is generated once the vein has been located, to control the transmission and reception probe in discontinuous mode and, from the changes in frequency between the transmitted and received ultrasonic waves, determine the diameter of the vein to ensure that its changes are displayed, and
an electrical power supply for the various electrical components of the device.
The subject of the invention is also directed at offering a novel method for measuring the change in diameter of a vein by the Doppler effect. According to the invention, the method consists of:
applying the transmission and reception probe of the device to the skin of the patient,
controlling the operation of the transmission and reception probe in continuous mode,
moving the transmission and reception probe on the skin of the patient until an audible signal is obtained corresponding to the location of the vein sought,
holding the transmission and reception probe in a fixed position,
controlling the operation of the transmission and reception probe in discontinuous mode in order to determine the diameter of the vein from the differences in frequency between the transmitted and received ultrasonic waves,
and displaying the changes in diameter of the vein.